With high functionality of mobile phones, digital AV equipment, IC cards, and the like, there is an increasing demand for high integration of silicon into a package due to decreases in size and thickness of a semiconductor silicon chip (hereinafter, chip) to be mounted. For example, a decrease in thickness is required in an integrated circuit, as typified by a chip size package (CSP) or a multi-chip package (MCP), in which a plurality of chips are formed into one package. In order to realize the high integration of chips into the package, it is necessary to decrease the thickness of the chip up to a range of 25 μm to 150 μm.
However, since a semiconductor wafer (hereinafter, wafer) serving as a base of a chip is thinned by grinding, the strength thereof is decreased, and thus there is a tendency for a crack or a warp to occur. In addition, since it is difficult to automatically transport the wafer of which the strength is decreased due to the thinning, the transportation has to be performed manually, which makes the handling thereof troublesome.
For this reason, a wafer handling system has been developed which bonds a plate-shaped member, referred to as a support plate, which is formed of glass, silicon, rigid plastic, or the like, to a wafer to be ground to supplement the strength of the wafer and which prevents a crack and a warp from appearing on the wafer. Since the strength of the wafer is supplemented by such a wafer handling system, it is possible to automate the transportation of the thinned wafer.
In the above-described wafer handling system, the support plate is bonded (temporarily fixed) to the wafer using various thermoplastic resins, adhesives, and the like. After the wafer having the support plate bonded thereto is thinned, the support plate is released from the wafer before dicing the wafer.
PTL 1 discloses a technique of suitably performing the temporary fixation and release of a support plate with respect to a wafer. In the technique disclosed in PTL 1, a laminate is used which includes a substrate to be ground, a bonding layer coming into contact with the substrate to be ground, a photothermal conversion layer including a light absorbent and a heat-decomposable resin, and a light-transmitting support, the photothermal conversion layer being decomposed when the irradiation with radiant energy is performed after the surface of the substrate to be ground on the opposite side to the bonding layer is ground, to thereby release the ground substrate and the light-transmitting support from each other. When the support plate (support) is temporarily fixed to the wafer (substrate) using the laminate, the photothermal conversion layer is irradiated with light, and thus it is possible to easily release the wafer and the support plate from each other.